The semiconductor industry continues to have a need to access numerous electronic devices on a semiconductor wafer. As the semiconductor industry continues to grow, devices become smaller and more complex. Many electrical devices, most commonly semiconductor devices and on-wafer electrical interconnects, are electrically tested. Some of these tests require sensitive measurements, with electrical isolation between channels of the probe card on the order of 1010 to 1014 Ohms. Some types of testing (e.g., reliability testing, or the like) may generally require long measurement periods, which can be in the range of several hours to several weeks. Reliability testing also generally includes a wide range in temperatures, which can be anywhere from about ambient to about 400° C. As the semiconductor devices get smaller, so do the contacts (generally referred to as pads) used to test the devices. Relatively smaller pads, which can be in the range of about 50 μm by about 50 μm (or even smaller), requires relatively smaller probes and relatively higher precision of probe alignment.
Multisite testing is one approach for increasing test sample size without further increasing the test durations. Multisite testing relies on testing relatively more portions of the semiconductor wafer simultaneously. Multisite testing, particularly multisite testing over a wide range of temperatures (e.g., about ambient to about 400° C. as mentioned above) includes additional challenges. For example, in order for a probe card to contact multiple sites on the semiconductor wafer over a range of temperatures, the probe card generally will need to change in size by about the same amount as the semiconductor wafer and generally must remain substantially flat over the various temperatures. Mismatches in expansion or changes in flatness of the probe card can cause positioning errors between the probes and the semiconductor wafer pads.
Probe cards are often constructed of a variety of materials, such as, but not limited to, metal alloys or the like for a probe card plate and ceramics or the like for a probe core. The materials are generally selected based on the low thermal expansion of silicon and ceramics in order to provide relatively high electrical isolation. The materials, however, generally have different coefficients of thermal expansion, which can cause a buildup of stress between the components, and can even cause shifting between the components. Unless the probe sites are adjustable, which is generally not the case due to the amount of time, limited access, and complexity involved, shifting is problematic as it affects the alignment between the probes and the semiconductor wafer pads. As a result, the components of the probe card assembly are generally bonded together. Bonding the components together can lead to deformation, and even fracture, of the components or the bonds between them when testing across a large temperature range.